Integrated gearbox lube and control system

ABSTRACT

A gearbox system includes a gearbox having integrated therein a pump system, a plurality of fluid passages and a clutch control system. The pump system is in fluid communication with the clutch control system via the fluid passages to flow at least one pressurized stream. A first pressurized stream controls a first pressure-responsive device included in the clutch control system. The gearbox system further includes a hydro-mechanical control unit (HMCU) in fluid communication with the gearbox to receive a second pressurized stream and to generate at least one actuator control stream. The actuator control stream controls an actuator integrated in the gearbox.

DOMESTIC PRIORITY

This application is a division of U.S. patent application Ser. No.13/711,137, filed Dec. 11, 2012, the disclosure of which is incorporatedby reference herein in its entirety.

BACKGROUND

A gearbox for an aircraft primarily functions to transmit rotationalpower through fixed engagements. A common gearbox lube system lubricatesand removes heat, where lube oil is typically sourced from an externalpumping system and is distributed within the gearbox. However, sometimesmultiple functionalities are required that can be difficult toincorporate together and then package into the gearbox. Thesefunctionalities can include gearbox lubrication and cooling, a clutch toengage and disengage the gearbox, control of a propeller blade pitchsystem, and electrical systems with control and sensing capabilities.

Where higher capability and system functionality are necessary, a higherlevel of complexity and integration effort is required. In addition, agearbox for an aircraft typically needs to operate at multiplealtitudes. These altitudes usually require various aircraft angles andsometimes zero to negative G operation, especially for militaryaircraft. A typical gearbox is commonly designed with these multiplealtitudes in mind. However, implementing multiple systems in a gearboxhas been traditionally been challenging.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the various embodiments is particularly pointedout and distinctly claimed in the claims at the conclusion of thespecification. The foregoing and other features of the embodiments areapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a schematic diagram of a gearbox hydraulic system according toan embodiment of the disclosure;

FIG. 2 is an enlarged view of a hydro-mechanical control unit includedin the gearbox system illustrated in FIG. 1; and

FIG. 3 is a flow diagram illustrating a method of controlling a gearboxhydraulic system according to an embodiment of the disclosure.

DETAILED DESCRIPTION

Referring now to FIG. 1, a gearbox system 100 is illustrated accordingto an embodiment. The gearbox system 100 may be utilized by an aircraft;however, the gearbox system 100 is not limited thereto and instead maybe utilized in other various systems including, but not limited to,land-based vehicles and naval vessels.

According to an embodiment, the gearbox system 100 includes a gearbox102 and a hydro-mechanical control unit (HMCU) 104. The gearbox 102 maytransfer rotational power generated by a rotating input shaft (notshown) to rotationally drive a propulsion system, such as a propellersystem (not shown) for example. One or more sub-systems may beintegrated within the gearbox 102. In at least one embodiment, thegearbox 102 includes a housing 105 having one or more sub-systemsdisposed therein. The sub-systems may include, for example, apressure-actuated hydraulic clutch that selectively engages and/ordisengages the gearbox 102 from the input shaft, a hydraulic system tohold and change propeller blade pitch, a gear and bearing system, athree stage pumping system to provide hydraulic control, lubrication andcooling, a reservoir, a deaerator, an accumulator to maintain hydraulicclutch control during zero to negative G attitude operation, a propellerpitch-lock valve to hydraulically lock the propeller blade angle duringzero to negative G attitude operation, and electrical systems to providehydraulic control and sensing for pressure and temperature.

Referring further to FIG. 1, the gearbox 102 includes a clutch controlsystem 106, a lubrication/cooling system 108, and an actuation system110. The gearbox 102 further includes a pump system 112 integrated inthe gearbox 102 that draws in fluid contained in a reservoir 113 anddelivers it to the clutch system 106, the lubrication/cooling system108, and the actuation system 110.

More specifically, the main stage pump system 112 comprises of apositive displacement lube pump 114, a system filter 116, a pressureregulating valve 117, and a plurality of fluid passages 118. The lubepump 114 draws solid fluid in from the reservoir 113 and flows it to thesystem filter 116 via one or more of fluid passages 118. In at least oneembodiment a plurality of fluid passages 118 is integrated within thegearbox 102. A check valve 119 may be disposed downstream from thesystem filter 116 to prevent the solid fluid from flowing backwardsduring shutdown and/or filter maintenance. The interconnected fluidpassages facilitate the interplay of all system elements, and maydeliver flow having various pressures such as low-pressure, mid-pressureand high-pressure. For example, low-pressure fluid may have a pressureranging from about 0 psi to about 300 PSI, mid-pressure fluid may have apressure ranging from about 300 psi to about 600 psi, and high-pressurefluid may have a pressure of about 600 psi and above. The lube pump 114is driven in response to rotational power generated by the rotatinginput shaft. The lube pump 114 generates a pressurized fluid flow ofabout 300 psi, for example. The reservoir 113 may include a temperaturetransducer 120 to monitor the fluid temperature therein, and one or morevents 121 to vent the reservoir 113 to atmospheric pressure. Further,the reservoir 113 may include various components to manage and/orservice the oil volume therein including, but not limited to, fluid filland spill ports, a fluid level sight glass, and a fluid drain plug.

The system filter 116 may include a filter bypass valve 122 thatbypasses fluid if the system filter 116 becomes blocked. The bypassedfluid may be passed on to the gearbox. The sump 124 may be vented toatmospheric pressure through one or more screened vents 126. The systemfilter 116 also includes a filter delta pressure indicator (FDPI) 128.The FDPI 128 may include a pressure indicator that indicates thepressure across the filter element during various operations including,but not limited to, impending bypass and imminent filter maintenance orreplacement.

After passing through the system filter 116, the fluid exits the gearbox102 and goes through an external air/oil heat exchanger 130 thatregulates, i.e., reduces, the temperature of the fluid. The regulated,i.e., cooler, fluid then re-enters the gearbox 102 and is received bythe pressure regulating valve 117. The pressure regulating valve 117regulates the flow and pressure of the conditioned fluid at thepredetermined pressure. The pressure regulating valve 117 may alsofunction as a relief valve, which bypasses all surplus fluid to the mainstage pump inlet. One or more pressure transducers 132 may be in fluidcommunication with a respective fluid passage 118 to monitor fluidpressure. For example, a pressure transducer 132 is disposed downstreamfrom the pressure regulating valve 117 to monitor the main stage fluidpressure as regulated by the pressure regulating valve 117. Theregulated fluid from the pressure regulating valve 117 is directed to aflow divider 134 that is integral to the core passage system. The flowdivider 134 is integrated in the gearbox 102, and divides the regulatedfluid into three control streams (S1, S2, S3). In at least oneembodiment, the flow divider 134 is formed integrally from an innersurface of the gearbox 102. The three control streams (S1, S2, S3) aredirected to the clutch control system 106, the lubrication/coolingsystem 108, and the actuation system 110, respectively, to controlvarious operations thereof as described in greater detail below.Accordingly, integrating the flow divider 134 in the gearbox 102 mayachieve one or more control streams that conveniently allow forintegrating one or more sub-systems, such as an actuation system, a pumpsystem, etc., within the gearbox 102.

The clutch control system 106 comprises a manifold 136 and anelectro-hydraulic servo valve (EHSV) 138. In at least one embodiment,the clutch control system is integrated in the gearbox 102. The manifold136 receives the first stream (S1) from the flow divider 134, andgenerates cooling, lubrication, actuation flow, and pressure that areselectively output to a hydraulic clutch 140. Accordingly, the clutch140 may be selectively engaged and disengaged as described furtherbelow. When the clutch 140 is engaged, the output shaft of the gearbox102 becomes synchronized with the constantly rotating input shaft. Whenthe clutch 140 is disengaged, the gearbox 102 is disconnected from therotating shaft. The gearbox 102 may further include a clutch transfercoupling device 142 that allows external fluid to pass into and throughthe rotating input shaft.

The EHSV 138 is in electrical communication with the manifold 136 and aremotely located clutch control module (not shown). The clutch controlmodule may output a control signal that indicates a desire toengage/disengage the clutch 140. The EHSV 138 receives the controlsignal from the clutch control module, and instructs the manifold 136 toengage/disengage the clutch 140. In the case where the clutch 140 is tobe engaged, the EHSV 138 converts a clutch control signal and provideshydraulic pressure and flow to the manifold 136. Based on the controlsignal, the manifold 136 delivers the actuation flow, and pressure toengage and synchronize the clutch 140. If the clutch 140 is to bedisengaged, the EHSV 136 terminates the clutch signal, which causes themanifold 136 to inhibit delivery of the actuation flow, and pressure. Asthe actuation flow and pressure decreases, the clutch 140 becomesdisengaged. The coolant and lubrication flows are fed continuouslyregardless of the clutch status.

The clutch control system 106 may also include one or more sensors,which provide feedback information to the clutch control module. Basedon the feedback information, the clutch control module may outputadditional control signals to the EHSV 138. It is appreciated thatalthough the embodiment illustrated in FIG. 1 utilizes the manifold 136and EHSV 138 to control operation of a clutch control system, the clutchcontrol system may be replaced with another type of actuation system tobe controlled using the manifold 136 and the EHSV 138.

In a case where the gearbox 102 is implemented in an aircraft system,the manifold 136 may further include two output ports 144, 146, thatattach to an accumulator 148 and the pressure transducer 150,respectively, which monitor the fluid pressure. During zero to negativeG attitude operation, the accumulator 148 discharges to continuehydraulic clutch operation. A check valve 152 may be provided inmanifold 136 to prevent fluid from returning into the distributionsystem, and excessively reducing the pressure used for clutch actuationwithin the manifold 136.

The lubrication/cooling system 108 receives the second stream (S2)output from the flow divider 134. In at least one embodiment, thelubrication/cooling system 108 is integrated in the gearbox 102. Thelubrication/cooling system 108 comprises one or more coolant components154 including, but not limited to, jets and orifices that lubricate andcool one or more gearing/bearing systems 156 operating in the gearbox102. For example, one gear/bearing system 156 may be associated with theclutch 140. Accordingly, the lubrication/cooling system 108 may delivercooled lubricating fluid to the gear/bearing system 156 to preventoverheating.

The gearbox 102 may further include a debris filter system 158. Thedebris filter system 158 may include a positive displacement scavengepump 160, a screened chip detector 162, and a deaerator 164. Leakage anddrainage fluid from various portions of the gearbox system 100, such asthe HMCU 104, clutch control system 106, manifold 136, gear/bearingsystems 156, etc., may be collected in the sump 124. The positivedisplacement scavenge pump 160 may be driven by the rotating inputshaft, and may flow fluid mixed with air from the sump 124 through thescreened chip detector 162, which collects and monitors debris in theair/fluid mixture. The air/fluid mixture is then sent through thedeaerator 164 that separates the air from the fluid. The separated airis directed back to the sump 124 and the solid fluid is directed intothe reservoir 113 such that processes performed by the pumping system112 may continue.

The actuation system 110 may be utilized to control and/or move varioustypes of pressure-responsive devices. According to an embodimentillustrated in FIG. 1, the actuation system 110 is integrated in thegearbox 102, and may be utilized to control a pitch of a moveablepropeller blade unit (not shown). Although one embodiment utilizes theactuation system 110 to control a pitch of a propeller blade unit, theactuation system is not limited thereto. The actuation system 110further includes a positive displacement actuation pump 168, an actuatortransfer coupling device 170, a propeller pitch-lock valve (PPLV) 172and an actuator, e.g., a pitch actuator 174. Accordingly, the actuationsystem 110 works together with the HMCU 104 to control the pitchactuator 174 and adjust the pitch of the propeller blade unit. Forexample, the HMCU 104 receives an increased fluid pressure output fromthe actuation pump 168, which is driven by the rotating input shaft, andgenerates an actuator control stream that provides fluid pressure forcontrolling a movement of the pitch actuator 174. The actuation pump 168may increase the fluid pressure of the third stream (S3), for example,from about 300 psi to about 600 psi or greater. As previously mentioned,although the actuator control stream is described above to control apitch actuator 174, the actuator control stream may be utilized tocontrol other types of actuators that control other types of mechanicalcomponents.

Referring now to FIG. 2, the HMCU 104 described above is illustrated ingreater detail. The HMCU 104 may include a second electro-hydraulicservo valve (EHSV) 176, a pressure regulating valve 178, and a selectorvalve 180, which all work to provide flow and pressure to the actuationsystem 110 to control the pitch of propeller blade unit.

The second EHSV 176 may operate similar to the first EHSV 138 discussedabove. More specifically, the second EHSV 176 may receive an electroniccontrol signal from a main actuator control module (not shown) locatedremotely from the HMCU 104. The electronic control signal generated bythe actuator control module may indicate a desire to adjust a mechanicalcomponent, such as the propeller blade unit, controlled by an actuator,such as the pitch actuator 174. In response to the control signal, theEHSV may control one or more valves, e.g., the pressure regulating value178, the selector valve 180, etc., to output a fluid control signal,which controls one or more actuation systems 110. The actuation system110 may also include one or more sensors, which provide feedbackinformation to the main actuator control module. Based on the feedbackinformation, the actuator control module may output additionalelectronic control signals to the EHSV 176.

The HMCU 104 may also include a pressure regulating valve 182. Thepressure regulating valve 182 may also serve as a bypass, which returnssurplus fluid to the reservoir 113. The actuator transfer couplingdevice 170 allows external fluid to pass into and through the propellerblade positioning actuator. During normal operation when the full supplypressure is present, the PPLV 172 allows actuation fluid to pass throughto control the pitch angle of the propeller blade unit. However, whensupply pressure is interrupted, as during zero to negative G altitudeoperation, the PPLV 172 hydraulically locks the propeller blade unit tohold at the last commanded angle set prior to experiencing theinterruption.

In at least one embodiment, the HMCU 104 may be set to an atmosphericpressure through the reservoir, where leakage and actuation return flowis delivered. Further, the HMCU 104 may include two ground actuationcheck connections 184 and one or more check valves 186, which may beconnected to an external control system (not shown) that may service thegearbox system 100. The check valves 186 may also be in fluidcommunication with the sump 124 to provide a separate drain paththereto.

Referring now to FIG. 3, a flow diagram illustrates a method ofcontrolling a gearbox hydraulic system according to an embodiment of thedisclosure. At operation 300, a pressurized solid fluid is flowed withinthe gearbox, i.e., internally. As discussed above, the pressurized solidmay be drawn from a reservoir and flowed internally throughout thegearbox using a main stage pump system. At operation 302, thepressurized solid fluid is divided into a plurality of control streams.In at least one embodiment discussed above, a flow divider is integratedinside the gearbox and divides the main pressurized solid flow deliveredby the pump system into a plurality of control streams. Each controlstreams is delivered to a respective pressure-responsive sub-systemsintegrated within the gearbox at operation 304. For example, a firstcontrol stream may be output from the flow divider to a clutch controlsystem, while a second control stream may be simultaneously output fromthe flow divider to an actuation system. At operation 306, one or morepressure-responsive components included in the pressure-responsivesub-systems are controlled according to the respective control stream,and the method ends. For example, the first control stream may control ahydraulic clutch included in the clutch control system, while the secondcontrol stream may control the operation of a hydraulic actuatorincluded in the actuation system. Accordingly, a gearbox hydraulicsystem may be provided, which includes multiple hydraulic sub-systemsintegrated within the gearbox.

While various embodiments have been described in detail, it should bereadily understood that the inventive concept is not limited to suchdisclosed embodiments. Rather, the embodiments may be modified toincorporate any number of variations, alterations, substitutions orequivalent arrangements not heretofore described, but which arecommensurate with the spirit and scope of the inventive concept.Additionally, while the various embodiments have been described, it isto be understood that features may be included only some of thedescribed embodiments. Accordingly, the embodiments are not to be seenas limited by the foregoing description.

What is claimed is:
 1. A method of controlling a pressure-systemintegrated gearbox, the method comprising: flowing pressurized fluidwithin the gearbox; dividing the pressurized fluid internally withrespect to the gearbox to generate a plurality of control streams;delivering each control stream among the plurality of control streams toa respective pressure-responsive system integrated within the gearbox;and controlling at least one pressure-responsive component included inthe respective pressure-responsive system using a respective controlstream.
 2. The method of claim 1, wherein the plurality of controlstreams includes a first control stream output to the clutch controlsystem and a second control stream output to a hydro-mechanical controlunit (HMCU).
 3. The method of claim 2, further comprising disposing thehydro-mechanical control unit (HMCU) in fluid communication with thegearbox to receive the at least one pressurized stream and to generateat least one actuator control stream.
 4. The method of claim 3, furthercomprising controlling a hydraulic clutch that selectively engages anddisengages the gearbox with respect to a rotatable input shaft via afirst control stream among the plurality of control streams.
 5. Themethod of claim 4, further comprising: disposing a hydraulic clutch influid communication with the plurality of control streams, the hydraulicclutch selectively operable in an engaged position and a disengagedposition based on fluid pressure; selectively outputting the firstcontrol stream to the hydraulic clutch; and delivering an electricalcontrol signal to the electro-hydraulic servo valve (EHSV); andoutputting the first control stream via the EHSV based on the electricalcontrol signal, the hydraulic clutch induced to the engaged position inresponse to receiving the first control stream and induced to thedisengaged position when the lacking the first control stream.
 6. Themethod of claim 5, delivering the at least one actuator control streamto an actuation system of the gear box in fluid communication with theHMCU to receive the at least one actuator control stream.
 7. The methodof claim 6, operating a second pressure-response device of the actuationsystem based on fluid pressure from the at least one actuator controlstream.
 8. The method of claim 7, wherein the second pressure-responsivedevice is a pitch actuator to control movement of a propeller bladeunit.
 9. The method of claim 7, further comprising controlling the HMCUin response to performing operations comprising: selectively outputs theat least one actuator control stream via a servo valve in response to anactuator control signal; and generating the actuator control signal tocontrol output of the at least one actuator control stream.
 10. Themethod of claim 9, further comprising dividing the pressurized fluid togenerate a third control stream, and cooling and lubricating a gear andbearing system of the gearbox based on a third control stream.